Induction of Resistance and Expression of Defense-Related Genes in Tobacco Leaves Infiltrated with Ralstonia solanacearum

Abstract

Ralstonia solanacearum 8107 (8107) is non-pathogenic to tobacco and elicits the hypersensitive response (HR). In Nicotiana tabacum cv. Samsun NN leaves infiltrated with 8107, acquired resistance to challenging tobacco mosaic virus (TMV) was induced 2-6 d after 8107-infiltration. hsr203J and hin1 genes were expressed only in the 8107-infiltrated area. On the other hand, the expression of PR-1a and PR-1b genes was not detected in the 8107-infiltrated area, but in areas other than that developing the HR. Expression of these PR-1 genes was regulated simultaneously and the kinetics of the expression was dependent on the distance from the infiltration area. Therefore, diffusible signal(s) might be produced in HR-causing cells and transmitted to peripheral cells resulting in expression of PR genes. In NahG10 tobacco infiltrated with 8107, the HR was induced but resistance to TMV was not. Analysis using NahG10 tobacco also showed that the salicylic acid (SA)-dependent signal regulated the expression of hsr203J and PR-1a, but not that of hin1 and PR-1b. These results suggest that resistance of tobacco to 8107 is SA-independent and involves a quite different mechanism from acquired resistance to TMV induced by 8107-infiltration which is SA-dependent.

The awr Gene Family Encodes a Novel Class of Ralstonia solanacearum Type III Effectors Displaying Virulence and Avirulence Activities

“…To better characterize the observed responses at the molecular level, we measured the expression of defense-related marker genes that are induced during development of HR in N. benthamiana. HIN1 was chosen as a specific molecular marker of HR in tobacco, because its expression is highly induced during incompatible interactions and strictly restricted to the challenged tissue (Gopalan et al 1996;Kiba et al 2003). Transcript levels of HIN1 and pathogen-response (PR) genes were measured by real-time quantitative reverse-transcriptionmediated polymerase chain reaction (RT-PCR) by using total RNA samples isolated from agroinfiltrated N. benthamiana leaves.…”

Isolation and expression analysis of candidate genes related to Ralstonia solanacearum-tobacco interaction

“…A leaf-inoculation method is widely used for analysis of molecular events during plant-bacteria interactions. Reproducibility of plant responses is confirmed in many plant-bacteria pathosystems, including the tobacco-R. solanacearum interaction (Kiba et al 2003). To improve the efficiency of inoculation, we inoculated tobacco leaves with R. solanacearum by leaf infiltration.…”

“…Samsun leaves and roots using the method previously described (Kiba et al 2003). Frozen tissues were homogenized in RNA extraction buffer consisting Tobacco plants were inoculated with R. solanacearum strain OE1-1 (RsOE1-1), 31b (Rs31b) and 8107 (Rs8107) by root inoculation and leaf inoculation.…”

Overexpression of a tobacco Dof transcription factor BBF1 stimulates the transcription of the tobacco mosaic virus resistance gene N and defense-related responses including ROS production

“…It was reported that gene expression of PR1a, PR1b, Hsr203j, and Hin1 in Samsun NN tobacco was upregulated during HR induced by p50 expression (Ogata et al 2012) as well as infection of avirulent Ralstonia species (Kiba et al 2003). Acidic PR1a and basic PR1b are defense marker genes in salicylic acid and jasmonic acid/ethylene signaling, respectively, and Hsr203j and Hin1 are HR marker genes.…”